Detection of trace amounts of water



June 25, 1968 J. R. HRABINSKI DETECTION OF TRACE AMOUNTS OF WATER FiledAug. 17, 1965 FIG. I

JOSEPH Ii! HEAD/N5!!! lA/VENTUR ATTOHNEY United States Patent Oficeassess Patented June 25, 1%68 3,389,967 DETECTION OF TRACE AMOUNTS OFWATER Joseph R. Hrabinslri, 1040 Woodbridge Ave., Fords, NJ. 08863Continuation-impart of application Ser. No. 274,812, Apr. 22, 1963. Thisapplication Aug. 17, 1965, Ser. No. 486,436

11 Claims. (Cl. 23-230) The present invention relates to methods andapparatus for detecting extremely small trace, e.g. 10 ppm. amounts oftotal (free and combined) water present in organic or inorganic liquidswhich are inert to phosphorus pentoxide and to methyl orange indicatorpaper. More particularly, this invention relates to unique test papercomprising methyl orange indicator paper coated with a thin layer offinely divided particles of phosphorus pentoxide. Yet more particularly,in a preferred embodiment, this invention relates to testing the saidorganic or inorganic liquids for minute, e.g. 10 p.p.m. amounts of waterby contacting a small test sample of the liquid with the said testpaper. Most particularly, in a preferred embodiment, this inventionrelates to testing organic or inorganic liquids for both free anddissolved water by disposing a strip of the said indicator paper above asmall test sample of the liquid in a closed container and observing anychanges in color over a period of a few minutes. Also, in a preferredembodiment this invention relates to a device for detecting minuteamounts of water in a liquid comprising a dry closed containercontaining (a) a gas inert to P methyl orange and to the liquid to betested under a sub- 0 stantial partial vacuum and (b) a strip of methylorange indicator paper coated with a thin layer of finely dividedparticles of phosphorus pentoxide held in an upper portion of thecontainer, the said container having means in a lower portion of thecontainer for providing an orifice through which liquid may be drawnunder the influence of the partial vacuum to partially fill thecontainer. This application is a continuation-in-part of Ser. No.274,812 filed Apr. 22, 1963, now abandoned.

The present invention will be extremely useful in a number ofapplications where at present no simple rapid test device is available.As is well known, all of the devices presently available for detectingwater in e.g. l0 p.p.m. quantities are complex, such as, for example,the Karl Fischer method and various other methods suggested in theliterature which for various reasons have not become commerciallyavailable. The following fields of use indicate the scope and need forthe present invention:

(1) Checking solvents for presence of Water in laboratory and industrialapplications, e.g. in metal alkyl catalyst polymerization reactionsextremely low Water level contents are required.

(2) Checking of gasoline, jet fuels, rocket fuels and solvents at tankcars, trucks and delivery sites, e.g. jet fuels may be checked forfreedom from both free water and dissolved water.

According to the present invention it has now been discovered that traceamounts of both free and dissolved water can be detected simply bycontacting the liquid With methyl orange indicator paper lightly coatedwith phosphorus pentoxide. In a preferred embodiment a critical featureof this invention is that an extremely thin layer (e.g. about oneparticle deep) obtained for example, by merely shaking or tumbling thepaper in a container containing a small amount of P 0 is used and theamount of liquid sample tested is small. Although the mechanism involvedin the present invention is not fully understood it is thought that thisprocedure is essential due to the various hydration states obtained withP 0 Thus, the ex tremely small amount of water present adds 1 mol ofwater per mol of P 0 which immediately activates the indicator paper.Additionally, no additional particles of P 0 either use up the availableWater or insulate the paper from the layer of particles next to thepaper. It is, of course, not intended to limit this invention in any wayby this explanation of the results obtained, the test paper and theprocess for using it being the invention taught.

In another preferred embodiment of the invention it has now beensurprisingly found that rapid sensing of extremely small amounts of bothfree and dissolved water in organic liquids can be obtained by disposingat least a part of the paper above the surface of the liquid in a closedcontainer. By this procedure very small amounts of water, e.g. levels ofparts per million can be sensed within short periods of time, e.g. 2minutes. For positive detection of the same levels by other proceduressuch as mechanical shaking of the present paper immersed in the liquid,times of to minutes are required. This discovery opens the use of thisinvention for a number of applications which now can be satisfied onlyby Karl Fischer analysis.

Another important application of this invention is in testing of fuelsand hydraulic oils for extreme altitute aircraft and rockets. At presentseveral methods have been disclosed for checking jet fuels, etc.delivered to aircraft just prior to flight for free Water. However, nomethods have been suggested which will determine the presence also ofdissolved water, particularly to the low levels described above. It is,therefore, considered that this invention is an important contributionto this field. At the temperatures prevailing in extreme altitudes anywater including dissolved water present in the fuel presents apossibility of freezing to form ice crystals which may block lines,screens and orifices in the fuel system and other systems of theaircraft or rocket. Another important contribution of a preferredembodiment of the present invention is that the commercially used testprocedures for detecting dispersed Water are subject to inaccuracies dueto the presence of various additives in the fuels. With the presentpreferred technique of disposing the indicator paper above the surfaceof the fuel or other liquid being tested so that the paper is onlycontacted by the vapors, not only are faster, more accurate readingsobtained but also these additives (usually having a low vapor pressure)r or the liquid being tested essentially does not effect the testresults. It is noted that obviously both fuels in which appreciablequantities of Water dissolve and fuels Which dissolve only minutequantities of water may be tested for total water content.

In various preferred embodiments test papers may be supplied:

(A) In separate small sealed vials 101' containers into which thesolvent sample may be introduced, e.g. by sealing the vials under apartial vacuum and breaking a fritted end off under the surface of theliquid so that an appropriate amount (determined by the degree ofsubatmospheric pressure) of the liquid is drawn into the vial.

(B) In a tightly stoppered bottle containing a number of test stripsfrom which the individual strips may be transferred to the liquid sampleto be tested in a dry box :or under other suitable precautions toprevent contamination during transfer from moisture in the air.

(C) Coated with a protective coating impervious to water which willdissolve in the particular type of organic liquid to be tested, or Whichmay be stripped or peeled off in the liquid to be tested.

(D) In stoppered bottles wherein the paper is disposed above the liquidwith, if desired, part of the paper in contact with the liquid.

It has now been surprisingly discovered that a unique extremelysensitive rapid activating indicating paper can be 3 prepared by lightlycoating methyl orange paper with P powder. The present paper is uniquein that other acid indicator papers tested, i.e. Congo red, Brilliantyellow, methyl orange, Blue lit-mus, pH (wide acid range) pared to thesize of the liquid sample the small amount of water, e.g. p.p.m.,present would be too much diluted to give a good accurate reading.Typical preferred sizes are for the vial 2 /2 in overall length by A2"in diameter,

hydrion paper, all gave relatively poor results when similar- 5 for thebottles 50 or 100 ml. ly coated with P 0 All of these papers testedincluding The present invention will be more clearly understood thepreferred paper of this invention are porous papers from a considerationof the following examples fully ilinfipregnated with a solution of theactive chemical and, illustrating this invention. 0 course, thorou hlried, i. r t i coating with the i g i j iig of molsture before 10Example l.Preparation of paper and detection 10 p.p.m.

Similarly, base indicator papers tested, e.g. Blue litmus Water in examor phenolphthalein papers coated with a mono particle T0 0 ml- Of ry lvnt h xane in a 500 ml. ball joint layer of barium oxide were lesssensitive than most P 0 glass graduate was added a strip of methylorange test coated acid indicator papers and far less sensitive than P pWhich had bfien Coated with a layer of z s- The the methyl orange paperof this invention. coating was accomplished by placing several strips ofthe The phosphorus pentoxide powder commercially availtest paper in avial containing a small amount of finely able for laboratory use issuitable for the present invendivided P 0 powder (laboratory grade) andshaking for tion. However, if desired, higher or lower purity powdersabout 1 minute. The contents of the graduate were shaken may be used.These powders should preferably be of such for 5 minutes, and it wasnoted that no change in color of fineness that they will all passthrough a sieve having the P p had Occurredopenings smaller than .125mm. and corresponding to The stopper was removed and on it was placed asmall which is usually referred to as 120 mesh to the inch mar p of H20(approximately .006 g Aftcl replacing terial. the stopper the hexane wasshaken vigorously for 2 min- It is noted that not only is the present:paper extremely utes. Very small but distinct orange spots were observedsensitive to water but it is also adapted to calibration to on theyellow paper, indicating that the water had been give reproducibleresults so that by correlating exposure detected. time to various colorchanges precise measurement of the This example establishes that thesensitivity of the test level of water present is possible. is good forat least .001% (10 p.p.m.) H O content (ap- The present invention willbe more clearly understood proximate since the actual drop used was notweighed; from a consideration of the accompanying drawings. instead adrop of comparable size was weighed .006 gm./ FIGURE 1 presents a sideview of a closed glass vial 1 500 gm. solvent 100 %=.0012%.) However, itshould having a sealed thin neck 2, the said vial containing a gas benoted that as compared to Example 2 this test is only inert to P 0methyl orange and to the liquid to be tested, an approximation to anactual test situation since the water e.g. dry air or N and containing astrip 3 of the methyl was not fully dispersed prior to contacting withthe paper. Organe indicator P P Coated with a thin layer of finelyExample 2.Different papers at the 10 p.p.m. H O level divided particlesof P 0 FIGURE 2 represents a side view in hexane of a vial 4 Similar inall respects to the vial simwn in Preparation of the test solvent-To 1liter of n-heptane URE 1 except that the seaied up 0f.the thm neck 5 h(which had been dried previously over molecular sieves) been p off thusOpgung i Vial wherefby E y 40 was added 0.0100 g. of distilled water.The bottle was contammg the Paper 6 1S pamauy fined with hqmd 7 thenshaken on a mechanical shaker for -3 hours to drawn under the influenceof the partial vacuum, e.g. 7 disperse the Water q beaker 8 cqntalmngthe Said hqmfj 9 to be Preparation of the test papers-Into each of 5test b0tt It i noted .that m pieferred emljoqlment the tles (4 oz. widemouth bottles, predried in an oven thin neck is of capillary tube SIZ'G,e.g. A drameter so @-120 C) was placed 1 strip of P205 coated test that.the.neck of t i 9 hfted of q i wl'th papers as follows (coated as inExample 1): the liquid for easier viewmg without llqllld draining from B1 Test a er the vial or appreciable moisture from the air entering the iM th 1 O p 2 liquid to confuse the reading. Alternatively, a wider neck,2 B rang 1 U i nllrant Yellow. e.g. /s d1ameter, may be used withoutloss of liquid by 3 con 0 Red draining as long as the vial is heldvertical since the weight 4 Blueg Litmu's of the liquid will besupported by a reduction in pressure 5 Math 1 Viola in the inert gas tothe extent necessary. FIGURE 3 prey sents a side view of a test bottle10 having a stopper 11, Experimental procedure.lnto each of the 5 testbotthe test paper 12 afiixed to the stopper or otherwise held tles wasplaced -50 ml. of the wet n-heptane (described in the dry vapor spaceand the liquid to be tested 13. In this above). The bottles were cappedand taped and the folembodiment the sample would be poured into thebottle in lowing observations were made.

11:45 a.m..- Added Solvent. Added Solvent Added Added Added a dry box toprotect the paper from moisture in the air.

FIGURE 4 presents a side view of a test bottle 14 having a stopper 15and a long loose strip of the test paper 16 extending above the liquidto be tested 17. It should be noted that in all the figures the vaporspace above the liquid is intentionally small. It the space were largecom- Example 3.-Test of dry (commercial grade) solvent hexane 50 m1.samples of dry (commercial grade, without special drying prior toexperiment) solvent hexane were placed in five ml. ball jointerhlenmeyer flasks with the following P coated test papers (coated asdescribed in Example 1). The flasks were then allowed to stand for thetime indicated 6 #2 was juggled around so that a portion of the paperextended above the surface of the liquid. Within 30 minutes the aboveliquid portion of the paper turned a dis- 1 N.R.=No reaction.

This example indicates that this sample of commercial solvent hexanecontained some water but much less than p.p.m. Also, that this amount ofwater gives a completely negative (not ambiguous) reading for 2 hours.

Example 4.--Detection 20 ppm. water in benzene To determine whether ornot the paper can detect trace amounts of dissolved H O in solvents two50 ml. samples of dry C H were taken from the same container. Samples #1contained a strip of P 0 coated methyl orange paper. (This is thecontrol sample.)

Sample #2 contained only the dry C H Into #2 was placed one microliterof, i.e. 20 p.p.m. H O. The sample was then shaken for 1 hour on amechanical shaker. After shaking, a strip of the H 0 detecting paper wasplaced in #2. Then both #1 and #2 were placed on the shaker for 4 hours.

After 4 hours no change occurred in #1 (control). After 2 /2 hours thepaper in #2 began to show faint traces of red at the edges. After 4hours sample #2 had sufiicient red tinting at the edges of the paper sothat the two samples could be distinguished readily.

After shaking overnight, no change was observed in #1 while #2 hadincreased considerably in red color.

Example 5.The vapor phase eifect50 p.p.m. H O in heptane The heptaneused in the following experiment was predried by percolating through acolumn of alumina and storing over Na ribbon.

From a 1 quart bottle of the dry heptane there was withdrawn 4 samples(-50 ml. each) of the dry solvent. These four portions of dry heptanewere then placed into test bottles each containing a methyl orange P 0coated strip of water detecting paper, prepared as in Example 1, andnumbered as samples 1, 2, 3 and 4. The bottles were then sealed withmelted wax.

After standing 24 hours, all four samples gave the same result. Noneshowed even a trace of color change.

For the second series of samples, some wet heptane was prepared asfollows. To 1000 ml. of dry heptane (referred to above) was added -.05ml. of H 0. The bottle was shaken vigorously for -5 minutes and thenallowed to stand overnight. On the following morning the bottle wasplaced on rollers and agitated (rolled) for 2 hours (-50 p.p.m. H O).

From this bottle of Wet heptane were poured four 50 ml. samples ofsolvent which were placed into 4 oz. test bottles containing a strip ofthe P 0 coated methyl orange water detecting paper and they werenumbered as samples 1, 2, 3 and 4. The bottles were sealed with meltedwax.

Within a few minutes the reddish color began to develop at the edges ofthe paper. The samples had been shaken gently by hand for about 2minutes and then set aside. After about 5 minutes it was observed thatin sample #4 where a portion of test paper had accidentally, due toshaking, ended up above the surface of the liquid, this portion of thepaper had reacted to give a red color much more rapidly than the portionof paper below the surface of the liquid.

After observing this effect, the test paper in sample tinct red whilethe rest of the paper showed only traces of red.

After standing for about 2 hours, not much change was observed exceptthat the above liquid portions of samples 2 and 4 became a noticeablydarker red.

Then sample #1 was arranged so as to allow a part of the paper to stickout above the liquid level. Within 30 minutes the above liquid part ofthe paper turned red. 7

Since relatively little color change had taken place in sample #3 foralmost 4 hours, it was placed on the shaker for /2 hour without anysignificant change.

Sample #3 was then arranged in such a position that the entire strip ofpaper was above the liquid level. The sample was then allowed to remainin this position for 1 hour. No significant change in color was noted.

Sample #3 was then arranged so that only a portion of the paperprotruded above the surface of the liquid. After 1 hour no change wasobserved and the sample was left overnight.

Also, the paper in #4 was inverted at 4:30 P.M. so that the red portionwas at the bottom of the bottle and a yellow portion was now exposedabove the surface of the liquid. The purpose of exposing a fresh yellowportion of the paper above the surface of the liquidis to see whetherthe color change has gone to completion.

The following morning:

( 1) Sample #3 did not react at the exposed area (i.e.

above liquid level) or the submerged area.

(2) Sample #4 did react at the exposed area but not at the submergedarea.

(3) Sample #1 showed no signs of reacting further either at the exposedor submerged area. This seemed to indicate that with completely drysolvent samples no color change (either on the exposed or submerged areaof the paper) takes place.

The question arising from the above data is Why did sample #3 fail toreact at the exposed area whereas sample #4 did react quite noticeably?This may have been caused by the fact that sample #3 underwent a /2 hourperiod of vigorous shaking on the mechanical shaker. This shaking periodmay have caused all the water to react but in such a Way that efficientcontact of the reacted P 0 with the paper was lost, i.e. the powder wasshaken off. Additionally, the color change which was obtained wasdistributed over the entire paper, thus making it rather difficult to beobserved when compared with a color change that is all localized in oneplace.

To check this point two additional samples of wet heptane prepared asabove described were tested as follows. Sample #1 was allowed to standwith a portion of the paper exposed above the surface of the liquid.Within /2 hour the exposed portion of #1 became dark red.

Sampe #2 was shaken vigorously on a laboratory shaker for /2 hour. Thesample was then allowed to stand with part of the paper exposed. Theexposed part did turn red but at a much slower rate than #1. Hence, oncethe water in the sample is consumed or partially consumed, it appearsthat the color change on the exposed area will not occur or will occurat a much slower rate.

'7 This increased color change may thus, in a preferred embodiment,decrease the amount of time necessary for detection of water, andincrease the sensitivity of the paper.

Example 6.Vapor phase efiect using different papers a 10 ppm. H O levelSolvent: n-Heptane from same batch as used for experiment to observe theeffect of different papers 10 ppm. H O level.

Test papers: Also from same batch as used for experiment to observe theeffect of different papers the 10 ppm. H O level.

Procedure: A strip of each test paper was placed into separate 2/02.wide mouth bottles (dried and purged with N Then 50 ml. of the wetheptane (10 ppm. H O) was poured into each bottle. The bottles were thencapped and shaken for 10 seconds and allowed to stand so that a V4"portion of the test paper protruded above the surface of ti e liquid.The following results were observed.

Sample identification for this experiment is as follows:

Sample #l-Dry benzene (100 ml.)

Sample #2-Consists of 500 ml. of C H (dry) to which was added 25microliters of H 0, i.e. 50 ppm. The bottle was agitated on a roller for1 hour to dissolve the H 0.

Sample #3-Consists of a 100 ml. sample of the prepared wet C H (#2).This sample was tested with prepared paper.

Sample #4Consists of 100 ml. of prepared wet C H (#2) to which was addeda small quantity of P Sample #5-Consists of 100 ml. of prepared wet C H(#2) to which was added a strip of untreated methyl orange paper.

Procedure.A 100 ml. sample of dry C H (#1) was tested for H O with astrip of treated paper. After 3 hours no presence of H 0 was detected.Hence the supply of C H was considered acceptable for the experiment.

A 500 ml. aliquot of G l-I was drawn and to it was added 25 microliters50 ppm. of H 0 and the bottle was Time Methyl Orange Brilliant Congo Red"Blue Methyl Yellow Litmus Violet l2:00 Added solvent and shookvigorously for 10 seconds 12:02...- Uppilr area turning Nit N.R N.R NR.

re 12:05.." Upperarca red YR N.R N.R NR. 12:10.. Uppnrarea deep NR Ndt25.11.-" NR.

rod. 12:l5 Lower area traces N R N.R N.R N.R.

of rec. l2:25 -same U.A. light black; N.R N.R NR.

L.A., N.R. 12:30 -as1ne -same U.A. darkening N.R NR.

12:40...- U.A. deep red;

L.A. inoreasin N.R. L.A.,

U.A. Increasing; U.A. increasing; N.R N.R.

.11---. Nfn. Same. N.R NR. Same N.R NR.

liquid) Example 7.Vapor phase efl'ect50 ppm. H O in benzene Thisexperiment was conducted to confirm that the results reported in thepreceding experiment are applicable also to benzene containing a smallamount of water (i.e. benzene is known to absorb relatively largeamounts of water compared to heptane).

\Vet benzene containing 50 ppm. water was prepared as described inExample 5. Three samples of the Wet benzene 50 ml. were tested with thewater detecting paper. In sample #1, the test paper was kept below theliquid level, in sample #2, the test paper was partially exposed abovethe liquid level, and in sample #3, the test paper was wetted with thesample but was entirely suspended above the liquid level.

All samples began to undergo a color change within several minutes.Sample #2 reacted more rapidly at the part of the paper above the liquidlevel, but the effect was not as pronounced as the previous experimentusing heptane. (By this is meant that the lower portion of the paper wasturning red also but not as fast as the upper part. After standing forseveral hours all three samples turned red and it was no longer possibleto distinguish the vapor state effect of sample #2.

Example 8.--Criticality of paper preparation procedure To determinewhether or not prepared H O detecting paper has any advantage ascompared to:

(l) A test for water conducted by adding untreated indicator paper to asample of solvent already containing P205.

(2) A test for water conducted by adding P 0 to a sample of solventalready containing untreated indicator paper.

agitated on a roller for 1 hour to dissolve the H 0. From this wet C Hwas drawn three 100 ml. samples (#3, #4 and #5).

To sample #3 was added a strip of treated paper. To sample #4 was addedsome P 0 and after 5 minutes of agitation a strip of untreated methylorange paper was also added. To sample #5 was added a strip of untreatedmethyl orange paper and after 5 minutes of agitation a small amount of P0 was also added. Results are as follows. (Samples 3, 4 and 5 wereplaced on a mechanical shaker and observed.)

After 5 min.:

#3- /3 of paper turned red.

#4-Traces of red at the edges.

#5Traces of red but more than #4. After min.:

#3 /2 of paper turned red.

#4Traces of red at the edges.

#5Freckled with tiny red spots. After min:

#3All red except 2 small patches of yellow.

#4Traces of red at the edges.

#5-Freckled with tiny red spots. After min.:

#3All red except 1 patch of yellow.

#4Traces of red at the edges.

#5-Freckled with tiny red spots. After min.:

#3-Completely red.

#4Traces of red at the edges.

#5-Freckled with tiny red spots. After min.:

#3Completely red.

#4Traces of red at the edges.

#5-Freckled with tiny red spots.

From these results it appears that treatment of the paper with P(coating operation) has a significant efiect on the test. It is notlikely that the different results were caused by a difference in theamounts 1 of P 0 present in the sample because samples #4 and #5 hadapproximately the same amount of P 0 present and yet they gavenoticeably different results.

Example 9.-Criticality of paper preparation procedure- Amount of P 0 Afurther comparison of results obtained by using coated paper withresults obtained by using uncoated paper. This experiment is almostidentical with that recorded in Example 4. Two points of difference are:

(1) Approximately double the amounts of P 0 were used in the uncoatedsamples (as compared to those in Example 4).

(2) There was no 5 min. shaking period before the final addition ofpaper and P 0 (respectively) to the uncoated samples.

Into 3 containers were placed 50 ml. of wet C H (500 ml. of dry C H +25microliters of HO). In sample #1 was placed a strip of coated paper.Into sample #2 was placed some P 0 and then a strip of uncoated paperwas added. Into sample #3 was placed a strip of uncoated paper and thensome P 0 was added. The amount of P 0 added to each sample (i.e. #2 and#3) was -double of that used in Example 4. A rough estimate of theamounts used for this experiment would be -30 mg.

All 3 samples were then placed on a mechanical shaker for 1 hour and thefollowing results were observed.

1 /2 min.:

#1Paper red at edges and ends. #Z-No change in paper. P 0 on the sidesof the bottle. #3-No change in paper. P 0 on the sides of the bottle. 4min.:

#1Red colored area increases upwardly from edges.

From these results it appears that too much P 0 is extremely deleteriousto the results, i.e. the excess P 0 reacted with the water and efficientcontacting or reaction with the paper was somehow prevented.

Example lO.-Vapor phase effect with partially evacuated test bottle Sixtest bottles containing P 0 coated methyl orange paper were preparedunder dry nitrogen atmosphere. Two of these bottles were used for thisexperiment. Sample No. l was the control and sample No. 2 was thepartially By a difference in the amounts of P205 present in the sampleis meant the amount of P205 on the coated (#3) sample as opposed to theamounts in samples #4 and #5.

evacuated test bottle. The experiment was conducted as follows:

The plastic cap of No. 2 was removed and replaced with a rubber stoppercontaining a glass tube and a length of tygon tubing approximately 12inches long and stopped off with a pinched clamp. The tubing wasattached to a vacuum line and the pinch clamp opened so that the testbottle was put under vacuum approximately 20 inches of mercury. Once thebottle was evacuated the plastic tubing was pinched olf close to theglass tube in the stopper. Then the rest of the tubing was cut off sothat a 3 inch length remained attached to the bottle. Approximately 200ml. of wet heptane containing 10 p.p.m. of water was poured into a 400ml. beaker. The tip of the tubing on No. 2 was submerged in the liquidand approximately 60 ml. of this solvent was drawn up into the testbottle. The tubing was then pinched off with the clamp and the sampleset on the shelf so that the vapor phase effect could be observed. Intosample No. 1 was poured approximately 60 ml. of the wet heptane from thebeaker and the bottle was capped off and placed on the shelf alongsidesample No. 2.

11:55-Solvent was added to both test bottle.

12: l0Vapor phase effect was noticeable in both samples. The colorchange was approximately the same.

l2z20-Red color becoming darker. Both samples reacting in the samemanner.

12:25-Vapor phase portion of both samples dark red. Some frecklingnoticeable in the liquid portions of both samples.

Example l1.Vapor phase elfect--Elfect of temperature It was also foundthat temperature, i.e. 25 C. and 40 C. does not seem to be critical incalibrating the amount of water present by the vapor phase efiect.Thu-s, calibration tables would not have to be adjusted for minordifierences in temperature. However, it is not intended to limit thisinvention to operation at any particular temperature range. Thus, theeffect of a wider variation in temperature on the vapor pressure of thewater can be used to increase the sensitivity of the test if desired.However, this example also indicates the unique and surprising elTectobtained with the present test paper;

Preferred liquids capable of being tested by the present inventiontechnique preferably by the vapor phase effect are any organic orinorganic materials preferably liquid C C hydrocarbons, and substitutedhydrocarbons, e.g. halogen substituted saturated hydrocarbons, olefins,diolefins, acetylenes, aromatics, alicyclic compounds, and halogen orother functional group substituted derivatives of these. It is notedthat using the vapor phase technique even materials not inert to P 0 canbe tested particularly if these materials have a low vapor pressure sothat the paper is not contaminated or deactivated and as mentioned aboveparticularly if they have low solubility for water. Specific rocketfuels capable of being tested are e.g. hydrazine, decahydroacenaphthene,etc.

Example 12.-Paper coated with protective coating against H O Aprotective coating for water detecting paper, for example, the papercould be butyl coated by dipping the active paper into a solutionprepared from butyl polymer dissolved in heptane. Both the polymer andthe solvent must be free of Water. After dipping the paper would beplaced in a vacuum oven in order to strip olf the heptane.

The paper so treated might be much more resistant to atmosphericmoisture and yet still retain its water detecting properties. Thecoating (protective) could be made of a variety of materials accordingto the solubility properties of the solvent being tested for water.

Preparation of butyl coated H O detecting paper.To make the coatingsolution 3 g. of high 'MW butyl polymer (uncured) was placed in 25 ml.of dry heptane. Both the butyl and the bottle were predried in an oven(air) for /2 hour. The C addition was made in a dry box. The polymer andsolvent Were then shaken for 1 hour. Most of the polymer remainedundissolved but enough did dissolve to give a viscosity of light oil.

The strip of paper was immersed into the coating solution twice and thenplaced in a heated vacuum oven to dry (20 in Hg).

Within 1 hour the paper had turned completely red and had to bediscarded.

Two possible reasons for the color change are:

(1) Water present in the butyl itself. (2) Exposure of the coated paperduring the drying operation.

Preparation of butyl coated H O detecting paper.The coating solution(butyl-C described above was shaken for -3 hours more to dissolve alarger quantity of the polymer. The viscosity increased and the solutionbecame very cloudy.

A strip of the H detecting paper was dipped into this solution 3 timesat 2 min. intervals. The paper was then placed in a heated vacuum oven(50 C. -30 in. Hg) to strip off the C After 45 min. in the vacuum, thesample was close-d in a bottle and inspected. Some red spotting wasobserved at the center of paper strip and the point at which the forcepsheld the paper during the dipping. After 48 hours almost the entireSample had turned red although a little strip of slightly yellow colorremained. This yellow strip was the portion of the paper that had thethickest coating of butyl. The uneven thickness was caused by formationof a bead of polymer due to excess coating material that ran down thepaper during the drying process. Although some color change wasobserved, this sample is a big improvement over that previously preparedand indicates that the method is practicable. After 72 hours, the stripof paper had turned completely red.

What is claimed is:

1. The process for detecting minute amounts of water in a liquid whichcomprises contacting the said liquid with a test paper comprising methylorange indicator paper coated with a thin layer of finely dividedparticles of phosphorus pentoxide for a sufiicient period to obtain acolor change when said liquid contains trace amounts of water.

2. The process of claim 1 in which the liquid is inert to phosphoruspentoxide and to methyl orange indicator paper.

3. The process of claim 1 in which the phosphorus pentoxide particlesare smaller than 120 mesh and the coating is essentially of 1 particlethickness.

4. The process of claim 1 in which the liquid is a liquid C Chydrocarbon.

5. The process for detecting minute amounts of Water in a liquid whichcomprises contacting a strip of methyl orange indicator paper coatedwith finely divided phosphorus pentoxide particles with vapors from thesaid liquid collected in a small confined space above the liquid toobtain a color change when said liquid contains trace amounts of water.

6. The process of claim 5 in which the liquid has low solubility forwater.

7. The process of claim 5 in which the liquid has high solubility forWater.

8. The process of claim 5 in which the liquid is a jet fuel.

9. The process of claim 5 in which the liquid is a C C liquidhydrocarbon.

10. A device for detecting minute amounts of water in a liquidcomprising a dry closed container under a substantial partial vacuum ofa gas inert to P 0 methyl orange and to the liquid to be tested,containing a strip of methyl orange indicator paper coated with a thinlayer of finely divided particles of P 0 disposed and held in an upperportion of the container, the said container having means in a lowerportion of the container for providing an orifice through which liquidmay be drawn under the influence of the partial vacuum to partially fillthe container.

11. A device for detecting minute amounts of water in a liquidcomprising a dry partially evacuated closed container containing a stripof methyl orange indicator paper coated with a thin layer of finelydivided particles of P 0 disposed and held in the upper portion of thecontainer and extending substantially into the lower portion of thecontainer, the said container having frangible means for providing anorifice through 'which liquid may be drawn to partially fill thecontainer.

References Cited UNITED STATES PATENTS 2,214,354 10/1940 Snelling 116114 2,249,867 7/1941 Snelling 73-335 2,487,077 11/ 1949 Shepherd 23-2322,567,445 9/1951 Parker 23230 2,844,025 7/1958 Joyce et al. 73-533,051,661 8/1962 Collins 252-408 OTHER REFERENCES Pennington, W.:Determination of Water in Freon 12, Analytical Chemistry, vol. 21, 1949,pages 766-9.

Cole et al.: Continuous Coulometric Determination of Parts per Millionof Moisture in Organic Liquids, Analytical Chemistry, vol. 31, 1959,pages 204840.

MORRIS O. WOLK, Primary Examiner.

Z. PAROCZAY, S. MARANTZ, Assistant Examiners.

1. THE PROCESS FOR DETECTING MINUTE AMOUNTS OF WTER IN A LIQUID WHICHCOMPRISES CONTACTING THE SAID LIQUID WITH A TEST PAPER COMPRISING METHYLORANGE INDICATOR PAPER COATED WITH A THIN LAYER OF FINELY DIVIDEDPARTICLES OF PHOSPHORUS PENTOXIDE FOR A SUFFICIENT PERIOD TO OBTAIN ACOLOR CHANGE WHEN SAID LIQUID CONTAINS TRACE AMOUNTS OF WATER.